Asphalt and Hydraulic Concrete Mix Design

Hydraulic Concrete

The study of the performances of the Hydraulic Concrete Archean of Man gneiss aggregates with the addition of filler to replace the basalt of Kasila group in the asphalt and concrete mix design of southern Sierra Leone is presented in this document. The goal is to compare the results of the asphalt and concrete Hydraulic Concrete mix design with gneiss and basalt aggregate. The applied methods and design used are 1) Volumetric design and Marshall method for the asphalt, 2) French Dreux-Gorisse Method for the concrete. We added 2% of gneissic filler and 2% portland cement type 42.5 R to the asphalt hot mix with the gneiss aggregates to follow the criteria variation. The Marshall, the diametric compression and the Duriez tests require us to perform four different types of mix design. The four mix designs meet the requirements but F2 and F4 give the best mechanical properties. F2 (gneiss + 2% filler) and F4 (basalt) have many similarities from which we can conclude their interchangeability. F2 gives 5255 of optimal bitumen content. In regards to hydraulic concrete, the results of the compressive strength test (cement content 350 kg CMI 42.5 R/m3) with the gneiss and basalt aggregates are respectively 40 MPa and 45 MPa at 28 days curing: these values are greater than 35 MPa required by the technical specifications. The use of the Super Fluid ® Thermoplast 120 admixture, to increase the concrete compressive strength, is justified by the requirement of a minimum of 80% Rc28 at 24 hours. For both types of concrete, we have at 24 hours, 34 and 35 MPa which are higher than the minimum of 32 MPa (in 24 h). These results meet the requirements of the technical specifications.

A good road network with good infrastructure is essential to create a suitable environment for economic development. In West Africa, some economically strategic areas are still isolated due to poor road conditions.

As part of the Mano River cooperation between Liberia, Sierra Leone and Guinea, it is planned to link Monrovia (Liberia) and Conakry (Guinea) via BO (Southern Sierra Leone).

In order to connect Liberia and southern Sierra Leone, the European Development Fund has financed the Bandajuma-Mano River section, which is 103 km long.

However, the Bandajuma-Mano river project crosses the gneiss of the Archean Domain of Man [1].

It is in this context that research is being conducted on gneiss as a substitute for the long-used basalt.

To meet the objectives of this study, the following will be carried out:

a) The geological overview will provide a presentation of the local geology of southern Sierra Leone.

b) Asphalt mix Design in addition to the Marshall tests, the water sensitivity will be evaluated by the Duriez test. Using a mathematical approach, elastic modulus values will be calculated to assess the behavior of asphalt mix design with the compaction level.

c) The Concrete mix design with gneiss aggregates will allow the determination of its compatibility with Portland cement and its performance compared with basalt aggregates.

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